This application outlines a continuing (years 7-9) research plan designed to elucidate the neuroanatomical organization of the corices (mesocortices) that form the so-called limbic lobe in the old-world monkey. The mesocortices form a large part of the cortex on the medial surface of the cerebral hemisphere, and well-know areas like the cingulate gyrus, parahippocampal gyrus, posterior orbitofrontal area and temporal polar area are major elements. The major long term goal is to understand their relationship with the neocortex. Three continuing aims are outlined: (1) the first, and major aim entails experimental neuroanatomical studies on the connections of the mesocortices using anterograde and retrograde tracing techniques, (2) the second aim centers around light microscopic reinnervation studies in deep temporal lobe structures like the amygdala, (3) the third aim is represented by studied that assess axon collateralization in mesocortica connections using fluorexcent double-labeling techniques. Connection studies address the intrinsic and commissural projection of the mesocortices, reinnervation studies focus on the lateral amygdaloid nucleus and double-labeling studies assess axon collateralization in the posterior parahippocampal, cingulate and orbito-frontal areas. The research has basic as well as clinical neuroscience relevance. The mesocortices are connectionally and architecturally intermediate in structure, sharing the features of interconnecting the association cortices with the limbic system. When this relationship is disrupted in neurological disease debilitating disorders relating to memory, attention and emotion results. The reinnervation studies focus on temporal lobe areas involved frequently in head trauma and hold relevance to post-traumatic changes in behavior seen frequently in the clinical setting. To conserve costs the individual investigations are designed in an interlocking fashion and draw in part on a collection of non-human primate material gathered over the past 15 years at Harvard Medical School (1969-1978) and the University of Iowa (1979-1984). None of the proposed investigations rely exclusively on the generation of all new research material.